FRESH-WATER DIATOMS FROM HIGH ARCTIC PONDS (CAPE HERSCHEL, ELLESMERE-ISLAND, NWT)

A taxonomic and preliminary ecological description is provided for diatom assemblages identified from the surficial sediments of 36 ponds from Cape Herschel (78-degrees 37'N, 74-degrees 42'W), on the east-central coast of Ellesmere Island. Physical and chemical limnological data indicate that, with few exceptions, the ponds are shallow, clear, oligotrophic, alkaline, and non-saline. A total of over 122 diatom taxa from 27 genera were identified, some of which are as yet undescribed. Benthic diatoms are abundant, whereas planktonic taxa are absent. Overall species richness on the Cape is high, but is low within each pond. Striking differences in species composition are evident amongst the ponds. A CCA (Canonical Correspondence Analysis) ordination indicated that Ca2+ and pH were the environmental variables most significant to the diatom flora but only accounted for 11.4% of the floristic variation. It is likely that benthic diatoms closely reflect substrate composition (e.g., rock, moss, sediment), rather than simply water chemistry. In addition, other factors, such as herbivory, are likely important in determining diatom species composition.